There is simple class:
class A(object): __COUNTER = 0 def do_something_1(self): ... def do_something_2(self): ... def do_something_N(self): ...
Is there decision which can increase self.__COUNTER by calling method but not write it to each function?
I want as something as:
a = A() # COUNTER = 1 b = A() # COUNTER = 2 c = A() # COUNTER = 3
To hook into methods being called you'd have to use a decorator:
def increment_counter(method): def wrapper(self, *args, **kw): self._COUNTER += 1 return method(self, *args, **kw) return wrapper and apply this to each of the methods in your class:
class A(object): _COUNTER = 0 @increment_counter def do_something_1(self): ... @increment_counter def do_something_2(self): ... @increment_counter def do_something_N(self): ... Note that I renamed the counter to use one underscore, to avoid having to figure out the mangled name.
If you must have __COUNTER work (so with the double underscore), you could do that by passing in the name of the class:
def increment_counter(classname): counter_attribute = '_{}__COUNTER'.format(classname) def increment_counter_decorator(method): def wrapper(self, *args, **kw): setattr(self, counter_attribute, getattr(self, counter_attribute) + 1) return method(self, *args, **kw) return wrapper Then decorate the methods with:
@increment_counter('A') def do_something_1(self): ... If you wanted to create a counter per instance instead, simply add to the counter on the class:
class A(object): _COUNTER = 0 def __init__(self): A._COUNTER += 1 or use type(self)._COUNTER if you want to use a separate counter per sub-class of A.
Here's the simple version: How to increment a class-wide counter every time a particular function is called. The function can be __init__, which covers your specific question.
class cls(object): counter = 0 def __init__(self): self.__class__.counter += 1 print self.__class__.counter a = cls() # Prints 1 b = cls() # Prints 2 As you can see, the trick is to increment self.__class__.counter, not self.counter. You can do that inside any member function.
But don't use names starting with a double underscore, because they have special meaning for python (unless you know and want the special meaning, of course). If you want to flag the counter as private, use a single underscore: _counter.
